In the production of insulated panels or containers, for example, of the general type disclosed in U.S. Pat. Nos. 3,416,692, 5,082,335, 5,252,408 and 5,273,801, it is known to place a panel of microporous insulation material, such as a rigid foam having extremely small open cells, within an envelope or bag of an air impervious flexible barrier film. A plurality of the open bags are then usually placed within a vacuum chamber which evacuates air from the foam, after which each bag is sealed while in the vacuum chamber. It is also known to evacuate a sealed insulation bag by attaching an evacuation tube to a sealed bag, for example, as disclosed in above-mentioned U.S. Pat. No. 5,252,408.
In the production of vacuum insulation panels such as disclosed in the above-mentioned patents, it is desirable to provide for rapid evacuation of the air from the microporous insulation media, especially from foam material within large panels, and to assure that substantially all of the air is evacuated from the media. It is also desirable to determine that an evacuated panel does not have any leakage before the panel is sealed and to provide for efficiently producing a vacuum insulated box-like container which has minimal panel joints in order to minimize thermal leak paths and provide the container with a maximum R value.
The present invention is directed to an improved vacuum insulated panel and container which have the maximum R value per inch of wall thickness and to an efficient and dependable method of producing such panels and containers. In accordance with preferred embodiments of the invention, a generally flat panel or box-like container is produced by forming parallel spaced grooves within a flat panel of rigid microporous plastics foam having open cells on the order of 150 microns or less. The foam panel is inserted into a partially sealed envelope or bag of gas impervious barrier plastics film material or the foam panels are formed into an open end box which is inserted into a bag of the barrier film material. The bag includes an integrally formed tubular evacuation portion and is sealed around the panel or box of the foam material.
The bag is then evacuated with a computer control evacuation system including a nozzle which is releasably sealed to the tubular evacuation portion of the bag. The grooves provide for rapid evacuation of the foam and for receiving the barrier film material during evacuation. The evacuation system senses the vacuum level within the bag during evacuation and automatically controls a set of valves which may provide for directing an additive gas into the foam after a very low level of the evacuation is attained. The evacuation system also checks or monitors the vacuum to assure a constant vacuum level within the bag before the bag is sealed, and thereby assure the production of high quality vacuum insulation panels or containers. A thin layer of rigid foam is applied in liquid form to the outer surfaces of the vacuum insulated panel and allowed to cure to provide the panel with thermal and mechanical protection as well as a panel with a uniform thickness and a smooth outer surface.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.